THz-NOMA beamforming aims at forming multiple beams of proper direction and width to serve multiple users. The half-power elevation and azimuth beam angles are inversely proportional to the SA beamforming gain [1]}, as illustrated in Fig. REF . For example, a beam with elevation and azimuth angular spreads of \(27^{\circ }\)  can have a SA gain of \([17.3]{dBi}\) , which is usually not sufficient for medium-distance communications [1]}. The probability of serving \(k\)  uniformly distributed users (polar uniform distribution) in an angular spread of \(27^{\circ }\)  is small (\(0.02\)  for \(k\!=\!2\) ; so an average of 100 users are required to serve two users per beam). Such observations raise concerns about the practicality of NOMA at high-frequency bands.
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